Guilin Sun
Ansys Employee

This is what the constraint mesh does. It specifies the max edge length in the region.

For the background mesh, it does not strictly enforce the min edge length specified. The finite element meshing begins from the max edge length, with constraints of mesh quality and iteration limit. It gradully refines the mesh with certain rules, based on doping, geomery, contact/active region etc.

To reduce memory requirement, you can also consider larger max edge length if there is large bulk material. also you can reduce the triangle quality ans sensitivity.